One role of the fuel cell separator is to confer each unit cell with electrical conductivity. In addition, separators provide flow channels for the supply of fuel and air (oxygen) to the unit cells and also serve as boundary walls separating the unit cells. Characteristics required of a separator thus include a high electrical conductivity, a high impermeability to gases, chemical stability and heat resistance. In household fuel cell applications in particular, long-term chemical stability is required.
Techniques for achieving these characteristics include the methods disclosed in Patent Documents 1 to 9.
However, in the methods of Patent Documents 1 and 2, because a resin having ester bonds is used in the fuel cell separator composition, hydrolysis may arise in the resin during power generation by the fuel cell, making the resistance of the fuel cell separator to hot water problematic. Moreover, curing of the composition takes a long time, and so these methods are also unsuitable for mass production.
In the methods of Patent Documents 3 to 7, because an epoxy resin having a high content of hydrolyzable chlorine is used in the fuel cell separator composition, the hydrolyzable chlorine lowers the crosslink density of the cured product, as a result of which the resulting fuel cell separator has insufficient heat resistance.
In the method of Patent Document 8, when triphenylphosphine is used as the cure accelerator, the resulting fuel cell separator has insufficient heat resistance. When 2-phenyl-4-methyl-5-hydroxymethylimidazole is used as the cure accelerator, owing to the poor compatibility between the accelerator and the epoxy resin, the curing reactions have difficulty proceeding, and so the resulting fuel cell separator has insufficient strength and heat resistance.
In the method of Patent Document 9, because triphenylphosphine is used as the cure accelerator, the resulting fuel cell separator has insufficient heat resistance.
Fuel cell separators are generally located in a working environment that is repeatedly subjected to wet heat and dry heat. When a fuel cell separator lacks adequate resistance to heat and hot water as in the case of the separators disclosed in each of the above patent documents, deformation and cracking sometimes arise during power generation within such an environment.